An electronic image forming apparatus such as a copying machine or a printer forms an image by transferring a developer image from a transfer belt or a photoconductive drum to a recording medium using a transfer device, and fixing the transferred developer image onto the recording medium.
The transfer device includes a transfer roller, and transfers the developer image to the recording medium by applying voltage to the transfer roller and pressurizing the same. The recording medium having the developer image transferred thereto is carried to a fixing device along a carrying guide.
Therefore, positioning of the transfer roller and positioning of the carrying guide downstream of the transfer roller in the recording medium carrying direction are required for achieving satisfactory transfer and avoiding paper jam.
The transfer roller and the carrying guide in the related art are mounted to an integrally formed holding member. The transfer roller is covered on its surface with a resilient member, and hence precision of external dimensions is not high.
Therefore, it is necessary to intensify load application to the transfer roller by a spring in the direction toward a transfer opposing roller or the photoconductive drum considering tolerances of external dimensions of the transfer roller. The holding member configured to hold the transfer roller is required to have a strength which can resist the load application. Therefore, increases in weight and manufacture cost are resulted.
With this regards, as a method of reducing the load application to the holding member, a method of holding both ends of the transfer roller by independently displaceable members is proposed.
However, the carrying guide cannot follow the movement of the holding member because the movement of the holding member is provided with flexibility. Therefore, a gap is formed due to a change in relative position with respect to the holding member, so that paper jam may occur because of entry of the recording medium into the gap.
Therefore, there is a demand for a transfer device, an image forming apparatus, and an image forming method in which positioning of the transfer roller and the carrying guide with high degree of accuracy is ensured.